This invention relates to the design of the heads of golf club irons. More particularly, this invention relates to the design of the heads of golf club irons by employing computer methods and modeling plus the optimization of parameters based upon desired characteristics specified by the operator.
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
A microfiche appendix consisting of 3 microfiche sheets having a total of 35 frames is included as part of the specification. The microfiche appendix includes computer program listings for the basic shape program and the back-weighting program.
The previously unpublished textual work entitled "Design of a Dynamically Matched Set of Iron Golf Clubs" authored by Terry Hartzell, is the subject matter of an application executed on Jun. 13, 1995 to register copyright in the United States Copyright Office. The subject matter of this work is incorporated into the present specification by reference and is referred to hereinafter as "Hartzell, 1994."
The mass properties of a golf club head play an important role in the golf shot. These mass properties include: the overall mass, the three coordinates of the mass center location (X.sub.m, Y.sub.m, Z.sub.m) and the six elements of the inertia tensor (I.sub.xx, I.sub.Xy, I.sub.xz, I.sub.YY, I.sub.YZ, I.sub.zz). (The inertia tensor is a 3.times.3 matrix which represents the mass moments of inertia of a solid body in three dimensions. While the inertia tensor has nine elements, the 3.times.3 matrix is diagonally symmetric, thus, only six of the elements are independent.) The mass properties influence both the golfer and the outcome of the shot in many ways. Specifically, they can affect the swing of the golfer, the energy transfer at impact, the behavior of the club while swinging and during impact, and how the golfer feels the impact. The general relationships between these quantities and their affect on the golf shot are widely recognized and discussed extensively in golf literature.
When designing the heads of golf club irons, the designer approaches his task having a general idea of a basic shape and the desired mass properties. While the designer has direct control over the geometry of the club head, obtaining the desired mass properties is very difficult, if not impossible, for two reasons: 1) the values of the mass properties are not readily apparent from visual inspection, and 2) no present design method exists that configures the club head based upon the specified mass properties. Therefore, only after a club head design is completed does the designer know through solid modeling or direct measurement if the desired mass properties have been obtained. (Solid modeling is defined as the graphical representation of a solid body using a computer such that it is geometrically and physically equivalent to the original body. A variety of computer analyses can be performed on the solid model with the results representative of the original body; for example, determination of the mass properties of a solid body.) The design process then becomes iterative in reaching the desired mass properties
Of the ten mass properties mentioned above, meeting the desired mass and mass center location is intuitive and an experienced designer can accomplish this quite well although to a limited degree of accuracy. When it comes to the elements of the inertia tensor, a very important parameter with respect to impact behavior, the designer at best can only influence the values of the elements. It is a near impossibility that the designer actually achieve the desired values. Therefore, club designers only consider general guidelines for inertia values. Further compounding the problem is the interdependence of all the mass properties on each other. Changing one of the mass parameters will almost certainly have an effect on many of the others. An additional burden is the constraint of iron club set matching such as swing weight and/or frequency matching.
Accordingly, it is an object of the present invention to provide a method for the design of a golf club head.
It is also an object of the present invention to provide a system for the design of a golf club head.
A further object of the present invention is to provide a scientific analytical method for the design of golf club heads which allows the designer to specify various mass properties for the club head and create club heads which meet the mass properties specified.
It is also an objective of the present invention to provide a tool for the design of the basic shape of golfclub heads based upon geometric specifications of the club face and hosel sections as established by the designer.
It is an objective of the present invention to provide the designer with control over the geometric and mass properties of the golf club head design.
An additional objective of this invention is to provide for the design of iron golf club heads based upon user-specified golf club head mass properties which include any or all of the following: the mass, the three coordinates of the mass center location, and the six components of the inertia tensor.
It is an additional object of the present invention to provide a method for the design of golf club heads which allows the designer to consider and specify mass moments of inertia including cross-products of inertia (the cross-products of inertia (Ixy, Ixz, Iyz) are the off-diagonal terms of the inertia tensor, and are generally ignored in the design of iron golf club heads).
An additional objective of this invention is to allow the designer to significantly increase the precision to which the mass properties are specified and ultimately obtained in the design.
It is also an objective of this invention to provide a method and a tool for implementing the method which establishes the configuration of the club face-hosel blend section to yield a smooth transition between the club face and hosel sections.
It is a further objective of this invention to provide a method for the control of the shape of the back-weighting of a golf club to develop a variety of designs.
It is also an objective of this invention to provide a method for designing a variety of dynamically equivalent golf club heads, i.e., club heads with similar mass properties, yet different shapes and geometries.
It is also an object of the present invention to provide the designer with a method for creating a set of club heads that are "matched" (equivalent) or have a predefined relationship to each other with respect to one or more of the mass properties in creating a set of golf clubs as in a set of irons.
Additionally, the present invention provides a graphical means for evaluating the designs of golf club heads.
It is also an object of the present invention to minimize costs and the time associated with the evaluation of a club design by providing a tool for the evaluation of a golf club head design prior to the construction of an actual club head.
In addition, the present invention provides a format from which to directly manufacture the club head as if utilizing a computer-numerical-control (CNC) machine in conjunction with suitable computer-aided-manufacturing (CAM) software.
As a further objective, the invention provides the designer control over the geometric and mass properties of irregularly shaped solids.
A method for the design of a golf club head according to the present invention includes the selection, by the designer, of dimensions which define the basic shape of the golf club head. Once the dimensions which define the basic shape of the club head are known, critical points on the golf club head may be located. Once the dimensions of the basic shape and the locations of the critical points are known, a model of the basic shape may then be displayed.
In addition, the method according to the present invention may further include the selection of desired mass properties, types of mass constraints and back-weighting parameters, all of which are determined by the designer. These specifications, in addition to the basic shape of the club head, permit the design of the back-weighting of the club head. Once the back-weighting has been designed, the final solid model of the golf club head which includes the basic shape combined with the back-weighting may be displayed via a computer terminal.
The dimensions which are originally selected by the designer to define the basic shape include full length of the hosel, length of the straight section of the hosel, outer diameter of the hosel at the junction with the club shaft, inner diameter of the hosel, outer diameter of the hosel at the base, rake angle of the club face, angle between the shaft and the bottom edge of the club face, inside height of the club head, outside height of the club head, total length of the club face, length of the bottom edge of the club face, thickness of the club face at the top, thickness of the club face at the bottom, club face bottom edge radius, club face top edge radius, and club face outer radius.
The critical points which are located and which are critical to the design and display of the basic shape include the connection points between the rounded end section and the straight section of the club face (P1 through P4), the locations of the centers of curvature for the end section of the club face (RP1, RP2, RP3), the connection points between the club face and the blend section (P5 through P8), the locations where the blend section joins the lower portion of the hosel (P9 through P12), and the points which locate the bottom, top, and beginning of the tapered section of the hosel (P13, P14, P15).
The desired mass properties which are selected by the designer may include any one or any combination of the following: overall mass, the mass center X-coordinate, the mass center Y-coordinate, the mass center Z-coordinate, and each of the six elements which make up the inertia tensor.
The mass constraints may be specified as either equality constraints or inequality constraints.
The back-weighting parameters which are specified by the designer include: the volume brick size, the minimum brick height, the maximum brick height, and the initial brick height (initial conditions).
The critical points which are required to create and display the back-weighting include: the points that define the profile of the club face within which the back-weighting is configured (P1 through P8, RP1, RP2, and RP3), the four corners of the bottom of each volume brick located within the plane of the club face boundary (PB1(I,J) through PB4(I,J) where I (row) and J (column) are the indices that locate each brick), and the four corners of the top of each brick (PT1(I,J) through PT4(I,J)).
In achieving the final solid model, the designer may employ finite element solid modeling methods, optimization algorithms, geometric influencing, and modification of the original criteria specified by the designer in order to obtain a different solid model.
The system which is used to perform the method according to the present invention, includes a computer loaded with a basic shape program and a finite element solid modeling and analysis program. The computer is also connected to a display. When the computer operates the basic shape program, the user-specified dimensions are retrieved from an input means such as a keyboard, computer disk drive, etc., as are known in the art. The computer, operating the basic shape program, then locates critical points on the club head. The computer then operates the finite element solid modeling and analysis program to retrieve the dimensions and critical points to then display a basic shape model. The display may include a video monitor or a printer. In addition, the computer includes a back-weighting program. When the computer operates the back-weighting program, the mass properties, types of mass constraints, and back-weighting parameters which are selected by the designer are retrieved from the input means and locations of critical points concerning the back-weighting are determined. The computer then employs the finite element solid modeling and analysis program to display a final back-weighted solid model of a complete club head on the display.
Briefly, the invention provides a method of creating and evaluating the geometric and dynamic characteristics of a golf club head design by employing computer methods and modeling plus mass property optimization.